Astellas Pharma has joined Merck & Co. in forming a collaboration with US biotech Ambrx for the discovery and development of novel antibody-drug conjugates (ADCs) against an undisclosed number of targets in oncology. Ambrx’s site-specific conjugation platform represents an advancement over first-generation ADC technologies and has the potential to optimise drug delivery to tumour cells. The deal will expand Astellas’ existing capabilities in the ADC field, which it gained with its 2007 acquisition of Agensys.